We have shown that with field sizes of 8 degrees or more, protanopes and deuteranopes have trichromatic vision, mediated by a rhodopsin photorecptor. We propose a full delineation of this large-field trichromacy, and a comparison of large-field trichromacy with small-field dichromacy. In addition, we plan to study observers who show evidence of a rhodopsin-mediated color vision system, namely the incomplete achromats. We will perform psychophysical studies using fields of 1 degree to 8 degrees visual angle. The specific studies we propose include: color matching, luminosity (by heterochromactic flicker photometry), wavelength discrimination, hue estimation, and threshold additivity.